Selector switch



June 20, 1944. w H HOLDEN I 2,351,967

SELECTOR SWITCH Filed June 18, 1943 2 Sheets-Sheet 1 F/G./ //6 cur THROUGH ESCAPEMENT MAGNET SPRING MOTOR 8 ESCAPEMENT nvvew TOR By W H T HOLDEN June 20, 1944. HOLDEN SELECTOR SWITCH Filed June 18, 1945 FIG. 2

2 Sheets-Sheet 2 .4. G. SUPPL Y INVENTO/P By WH 7. HOLDEN Patented June 20, 1944 SELECTOR SWETCH William H. T. Holden, Woodside, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application June 18, 1943, Serial No. $1,274

Claims.

This invention relates to telephone systems and more particularly to an improved form of automatic switching apparatus for use in automatic or semiautomatic telephone systems.

In step-by-step telephone systems employing two-motion automatic switching apparatus, it has been customary to employ two operating magnets and brush sets all of which wipe over the terminal banks.

The use of a constantly acting power source with a digit impulse controlled escapement for such a two-motion switch has been proposed heretofore.

In accordance with the present invention a power driven shaft is provided controlled by an escapement mechanism. This power driven shaft carries two cams which serve to operate the horizontal and vertical stepping mechanisms. Each of these mechanisms comprises two sections, and a change-over mechanism is provided which interposes a finger between the sections of one or the other stepping mechanism in accordance with the direction in which the switch is to be moved.

Further, in order that noble metal may be used for the contacts in the talking circuit, the tip and ring brushes are arranged so that they may be positioned with relation to the desired bank terminals and a camming device is provided to move the brushes vertically into contact with the associated bank terminals.

These and other features of the invention will be more readily understood from a consideration of the following description in connection with the accompanying drawings in which:

Fig. 1 shows a perspective view of the essential parts of the switch structure;

Fig. 2 shows a circuit arrangement for operating the switch; and

Fig. 3 shows the spring winding circuit.

Referring first to Fig. 1, the switch itself resembles a standard step-by-step, two-motion switch in that it comprises sets of arcuate bank terminals, a brush rod centered with relation to the bank terminals and vertical and horizontal ratchet elements for controlling the corresponding motions of the brush rod. In general, no attempt has been made to show the mounting means for the Various parts of this switch since any convenient means may be used and its disclosure would only serve to confuse the drawings.

The contact terminals are arranged in three separate banks I00, IOI and I02, each containing the terminals of one of the three trunk conductors terminating in the switch. Centered with respect to banks I00 to IE2 is brush shaft I03. The double sleeve brush I04 is mounted directly on brush shaft I03. The single tip and ring brushes I05 and I06 are mounted on a sleeve ID'I which surrounds brush shaft I03. Pins I08 and I09 on shaft I03 enter slots in sleeve Ill! so that the tip and ring brushes I05 and I06 are raised and rotated in the same manner as sleeve brush I04. However, the brushes are so positioned on the shaft and sleeve that when they are raised to a particular level and then rotated, sleeve brush Iil i wipes over the terminals in that level, while the tip and ring brushes I05 and I06 move around below the terminals of the corresponding level. It is to be noted that brushes I06 and I05 are provided with relay type contact elements, referably made of noble metal. The corresponding bank terminals are similarly provided with noble metal contact elements. Near the upper end of the brush shaft I03 are located the rotary ratchet cylinder H0, and the vertical ratchet element III. Double dog H2 engages the teeth of the two ratchet elements to hold the shaft I03 in position and is controlled by release magnet II3. The upper end of shaft I03 passes through plate H4 and restoring spring II5 to the top of which it is fastened. On plate H4 is mounted rod H9 for guiding the upper end of shaft I03. A cam drive rod I It extends through brush shaft I03 and at its lower end is fixed to cam I I1. Pin IIB resting on spring Ii5 prevents rod IIB from moving longitudinally with respect to shaft I03. The lower end of sleeve I07 has a cammed surface which conforms to the configuration of cam iII when both rod I I6 and sleeve I01 are normal.

The power for driving the switch comprises a spring, like a clock spring, which is rewound by a miniature motor whenever the tension drops below a value suificient to carry the switch through a cycle. This spring and motor have been indicated at 26. The spring acts on drive shaft I2I and the rotation of the shaft is controlled by an escapement magnet 222. Any desired form of motor wound spring and escapement may be employed but one possible form is disclosed in the copending application of C. N. Hickman, Serial No. 475,380, filed February 10, 1943.

Drive shaft I2I carries three discs I23, I24 and I25. Disc iii-l is provided with a cam I26 which, once during each revolution, opens the normally closed contact between springs I21 and I28. Disc I24 is mounted eccentrically so that once during each revolution it moves bar I29, forming part of the rotary stepping mechanism. Disc I25 has a vertical camming surface I which acts on arm I3I forming part of the vertical stepping mechanism. Therefore at each revolution of drive rod I2I both the horizontal and vertical stepping mechanisms are acted upon by their respective cams.

Each stepping mechanism comprises two bars, one carrying the stepping pawl and the other acted on by the driving cam. On one bar is mounted a recessed member and on the other a correspondingly positioned projection, and when the stepping mechanism is ineflective the projection enters the recess without transmitting the motion of one bar to the other. When the mechanism is to be eflective a finger is interposed between the projection and the recess and the movement of the one bar under the control of the driving cam is transmitted to the second bar and thence to the stepping pawl and the switch.

Specifically, the vertical stepping mechanism comprises bar I3I which is acted on by cam I30 and bar I32 which operates the vertical pawl I33. Two projections on bar I32 are bent downward to form recess I34 while a vertical projection I35 is formed on bar I3I and both bars are so mounted that projection I35 is in position to enter recess I34 when bar I3I moves. Similarly the horizontal stepping mechanism comprises the bar I29 which is acted on by the disc I24 and bar I31 which operates the rotary pawl I38. Mounted in any suitable manner on bar I31 is a member having a recess I39 while projection I40 is formed on bar I29. Bars I29 and I31 are so arranged that projection I40 is in position to enter recess I39 when bar I29 is moved.

In order to transmit the motion of the moving bar to the pawl carrying bar, fingers I36 and MI are provided. These fingers are attached to rod I42 which is pivotally mounted on suitable supports I43 and I44, A part of rod I42 is broken away to show the apparatus behind it. Attached to the upper end of rod I42 is a bracket I45 formed integrally with the armature I46 associated with the magnet coil I41. At the other end of the armature is a. stud I48 which controls a set of relay type contacts I49. When the coil I41 is deenergized, rod I42 occupies the position shown and finger I36 extends across the recess I34. Therefore, when bar I3! is raised by cam I30, projection I35 does not enter recess I34, but acts through finger I36 to raise bar I32 and raise brush shaft I 03 by means of pawl I33.

When the magnet coil I41 is energized the rod I42 is rotated, moving finger I36 beyond recess I34 and moving finger I4I into position between projection I40 and recess I39. When cam I24 is rotated, acting on bar I29, the motion is transmitted to bar I31 which rotates brush shaft I03 by means of pawl I38.

In order to bring brushes I05 and I06 into contact with the terminals adjacent to which they have been positioned by the action of the stepping mechanisms, means is provided to rotate rod H6 and thereby cam II1. Clamped to the top of rod [I6 is a link I5I which carries rod I52. The armature I53 associated with magnet coil I50 is pivoted on pin I54 and terminates in a fork I51 which embraces rod I52. When the magnet coil I50 is energized, attracting armature I53, fork I51 moves fod I52 laterally, thereby creating a rotary motion of rod H6, in turn rotating cam II1. Since sleeve I01, carrying brushes I05 and I06, is held against rotation by pins I08 and I00, but may move vertically due to the slots in which pins I08 and I00 are engaged, the rotation of cam II 1 raises sleeve I01 and creates a relay type closure between brushes I05 and I06 and their corresponding contacts. The armature I53 associated with coil I50 also carries a stud I55 which acts on a set of relay type contacts I56.

In Fig. 2 is shown a suitable circuit arrangement for controlling the switch structure of Fig. 1. This circuit includes rotary normal contact I63, vertical olT-normal contacts I10, I1I, I12, and eleventh rotary step contacts I61 which have not been shown in Fig. 1 since they are wellknown parts of a standard step-by-step selector switch.

The circuit for the motor I6I which winds the driving spring I60 is shown in Fig. 3. Spring I60 unwinds in operating the switch and lug I62 on spring I13 is so positioned that the spring I60 will exert pressure thereon after it has completed the driving of a switch through a predetermined number of steps. The pressure of spring I60 on lug I62 closes contacts I14 and I15, completing a circuit connecting the motor I6I to the alternating current supply whereby the spring is rewound, ready for the next seizure of the switch. As the spring tightens, pressure is removed from lug I62 and contacts I14 and I15 reopen to in turn open the circuit of motor I6I. Spring I60 should be so designed as to be capable of operating the switch through several cycles without rewinding in case of a temporary power failure. Spring I13 and lug I62 should be so positioned that normally the spring will be rewound after each call requiring an average number of steps of the selector.

When the selector is seized, line relay I64 operates in a circuit from battery through the upper winding of relay I64, contact 2 of magnet I50, ring conductor I65 and thence over the calling substation to tip conductor I66, contact 3 of magnet I50, lower winding of relay I64, over normal contact I of the eleventh rotary step springs I61 to conductor I16. If the selector being described is a first selector, coupled with a line finder, conductor I16 will lead to ground through a source of dial tone, while if the selector is serving as a subsequent selector, conductor I16 will be grounded directly.

Line relay I64 operates in the above-traced circuit and closes an obvious circuit for slow-torelease relay I68. Relay I68 operates and connects ground to conductor I 69 to mark the selector busy and to hold any preceding selectors.

When the dial at the calling substation is oper ated, relay I 64 releases at each interruption of the line circuit, closing a circuit from ground, back contact of relay I 64, inner front contact of relay I 68 to the winding of relay I69 and battery, and in parallel therewith over contact I 10 of the vertical off-normal springs, back contact of magnet M1 to battery through the winding of escape magnet I 22. Relay I 69 operates and at its front contact closes a substitute for contact I10 which opens as soon as the brush shaft moves off normal. Escape magnet I22 releases the drive shaft I2I which makes about threefourths of a revolution when it is arrested. During this movement the vertical stepping mechanism is operated and the brush shaft lifted one step. When the dial recloses and relay I 64 reoperates, the escape magnet I22 releases and the drive shaft I2I advances to normal. Relay I69 is slow to release and remains operated, holding the circuit of the escape magnet I22 closed between dial pulses. The following pulses cause the selector to advance one step for each pulse.

At the end of the digit, relay I64 remains operated and relay IE9 is permitted to release closing a circuit from ground at its back cantact, contact 4 of magnet I50, contact I1I, through the winding of change-over magnet I41 to battery. Change-over magnet I41 operates, disabling the vertical stepping mechanism and rendering the rotary stepping mechanism operative as described in connection with Fig. l. Magnet I41 also closes a circuit from battery through the winding of escape magnet I22, front contact of magnet I41, contacts I28 and I21, controlled by the drive shaft in response to the operation of magnet I22, to ground at the rotary normal spring I63.

Magnet I22 operates in this circuit releasing the drive shaft which, as before, makes threequarters of a revolution during which the brush shaft is rotated on step, and the contacts I21 and I28 are opened to release magnet i2: and to permit the drive shaft to complete its revolution back to normal.

After one rotary step by the brush shaft, rotary normal contact I03 is opened and sleeve brush I04 is in contact with the sleeve terminal of the first outgoing trunk. The circuit of magnet I22 now extends from contacts I21 and I25, through the winding of magnet I50, contact 3 of eleventh rotary step spring I61 to ground at the front contact of relay 7 I60. In shunt of the winding of magnet I50 a branch circuit extends over contact 1 of magnet I50 to sleeve brush I04. If the first trunk is busy, ground will be connected to the associated sleeve terminal, magnet I50 will be shunted and magnet I22 will reoperate to cause brush I04 to be advanced to the sleeve terminal of the next trunk.

When an idle trunk is found the shunt around the winding of cut-through magnet I50 is opened and that magnet operates in series with magnet I22. Magnet I22 cannot operate through the winding of magnet I50 and the brush shaft remains in position with the sleeve brush I04 engaging the sleeve terminal of the idle trunk.

Cut-through magnet I50, in the manner described in connection with Fig. 1 now presses tip and ring brushes I05 and I06 against the corresponding tip and ring bank terminals, extendlng the calling line to the next selector. At its contacts 2 and 3, magnet I50 disconnects line relay I64 from the conductors I65 and I06, and relay I64 releases, opening the circuit of relay I58. At its contact 'I magnet I50 disconnects brush I04 from the circuit of magnet I22 and at contact 6 connects brush I04 to the incoming sleeve conductor I69 and to ground at the front contact of relay I68. Relay I68, being slow to release, holds ground on conductor I69 and brush I04 until after ground is supplied thereto from the next selector. At contact 5 magnet I50 opens the circuit of release magnet I I3. At contact 4 magnet I50 opens the circuit of changeover magnet I41 which restores.

At contact I magnet I50 closes a holding circuit for itself from battery through the winding of escape magnet I22, contact I and winding of magnet I50, contact 3 of eleventh rotary step spring I61, contact 6 of magnet I50 to ground over brush I04. The talking circuit and switch are therefore held under the control of magnet I50.

When the conversation is terminated, the release of the connector removes ground from brush I04, releasing magnet I50. Magnet I50 closes a circuit. from battery through the winding of release magnet II3, contact 5 of magnet I50, vertical off-normal contact I12 to ground at the back contact of relay I68. Magnet II3 withdraws the double dog from the ratchet elements and the brush shaft rotates to normal under the control of spring H5 and then returns to normal in the vertical direction under the force of gravity. When the vertical off-normal springs are restored, the circuit of release magnet II3 is opened and the double dog holds the brush shaft in its normal position.

If all trunks of a level are busy, the switch continues to rotate until the eleventh rotary step contacts I51 are operated. At contact 2 spring I61 connects busy tone from conductor I11 to the lower winding of line relay I64 and the tip conductor I66 to inform the calling subscriber that the call could not be completed. At contact 3, spring I61 disconnects ground from the windings of magnets I50 and I22 to prevent the operation of magnet I50 when brush I04 steps off the last busy terminal. When the subscriber restores his receiver relay IE4 releases, opening the circuit of relay I08. Relay I68 releases slowly, and, when it closes its back contact, operates release magnet II3 to restore the selector to normal.

It will be apparent from the foregoing that the novel switch operating means of applicants invention may be substituted for a conventional switch with a minimum of change in the operating circuits.

What is claimed is:

l. A two-motion step-by-step switch comprising a brush carrying shaft, a vertical ratchet mechanism for imparting vertical movement to said shaft, a rotary ratchet mechanism for imparting horizontal movement to said shaft, a power driven rotatable cam shaft having a first and a second cam mounted thereon, a vertical selecting finger positionable between said first cam and said vertical ratchet mechanism for imparting the movement of said cam shaft to said vertical ratchet, a rotary selecting finger positionable between said second cam and said rotary ratchet mechanism for imparting the movement of said cam shaft to said rotary ratchet, an escapement device for causing said cam shaft to make one revolution with each operation of said escapement device, and means for controlling the positioning of said vertical and rotary selecting fingers.

2. A two-motion step-by-step switch comprising a brush carrying shaft, a vertical ratchet mechanism for imparting vertical movement to said shaft, a rotary ratchet mechanism for imparting horizontal movement to said shaft, a power driven rotatable cam shaft having a first and a second cam mounted thereon, a vertical selecting finger normally positioned between said first cam and said vertical ratchet mechanism for imparting the movement of said cam shaft to said vertical ratchet mechanism, a rotary selecting finger positionable between said second cam and said rotary ratchet mechanism for imparting the movement of said cam shaft to said rotary ratchet mechanism, an escapement device for causing said cam shaft to make one revolution with each operation of said escapement device, and means for simultaneously removing said vertical selecting finger and moving said rotary selecting finger into position between said second cam and said rotary ratchet mechanism.

3. A two-motion step-by-step switch comprising a brush carrying shaft, a vertical ratchet bar for imparting vertical movement to said shaft, a rotary ratchet bar for imparting horizontal movement to said shaft, a recessed member on each of said ratchet bars, a power driven rotatable cam shaft having a first and a second cam mounted thereon, a first and second cam bar acted on by said cams, each cam bar having a projection thereon, said ratchet bars and said cam bars being so arranged that the projections on said cam bars may enter the recesses of said ratchet bars at each rotation of said cam shaft without imparting motion to said ratchet bars, a vertical selecting finger positionable between the projection on said first cam bar and the recess of said vertical ratchet bar for imparting the movement of said cam shaft to said vertical ratchet bar, a rotary selecting finger positionable between the projection on said second cam bar and the recess of said rotary ratchet bar for imparting the movement of said cam shaft to said rotary ratchet bar, an escapement device for causing the cam shaft to make one revolution with each operation of said escapement device, and means for controlling the positions of said vertical and rotary selecting fingers.

4. A two-motion step-by-step switch comprising an arcuate bank of terminals divided into three sections, a brush shaft, means for imparting vertical and rotary movement to said shaft, 9. first brush mounted directly on said brush shaft in position to wipe over the terminals of one of said bank sections, a pair of brushes mounted on a sleeve surrounding said brush shaft, means for holding said sleeve to said brush shaft so that the brushes carried by said sleeve move in accordance with the movement of said brush shaft, said pair of brushes moving out of engagement with the other two sections of said contact banks, a rod passing through said brush shaft, and means under the control of said rod to move said pair of brushes into engagement with the corresponding terminals.

5. A two-motion step-by-step switch comprising an arcuate bank of terminals divided into three sections, a brush shaft, means for imparting vertical and rotary movement to said shaft, is first brush mounted directly on said brush shaft in position to wipe over the terminals of one of said bank sections, a pair of brushes mounted on a sleeve surrounding said brush shaft, means for holding said sleeve to said brush shaft so that the brushes carried by said sleeve move in accordance with the movement of said brush shaft, said pair of brushes moving out of engagement with the other two sections of said contact banks, a rod passing through said brush shaft, a cam fixed to said rod and a camming surface on said sleeve, and means to rotate said rod to move said pair of brushes into engagement with the corre-- sponding terminals.

WILLIAM H. T. HOLDEN. 

